Laminated paper with reinforcing scrim

ABSTRACT

AN EXTENSIBLE, REINFORCED LAMINATED PAPER SHEET HAVING THE CHARACTERISTIC OF WITHSTANDING SUBSTANTIAL IMPACTS, FORMED BY TWO SUPERIMPOSED SHEETS OF EXTENSIBLE PAPER BONDED TOGETHER BY A LAYER OF HOT-MELT LAMINANT HAVING A SCRIM OF POLYESTER FIBERS EMBEDDED THEREIN WHICH TRANSMITS STRETCHING FORCES THROUGH THE SHEETS OF PAPER TO POINTS REMODE FROM THE ZONE OF IMPACT TO SUBSTANTIALLY REDUCE THE DEFORMATION OF THE EXTENSIBLE PAPER SHEETS IN THE AREA OF IMPACT.

June 20, 1972 P. HOFFMAN 3,671,372

LAMINATED PAPER WITH REINFORCING SCRIM Filed April 27; 1970 FlG. 5 4Z IN VENTORA PA U L` f-l oFF/)MAJ @mW/ma Afrox Eur United States Patent O1Tree 3,671,372 Patented June 20, 1972 3,671,372 LAMINATED PAPER WITHREINFORCIN G SCRIM Paul Holfman, 714 SW. 16th Ave., Gainesville, Fla.32601 Filed Apr. 27, 1970, Ser. No. 32,275 Int. Cl. B29h 9/04; B32h 5/04U.S. C1. 161-58 16 Claims ABSTRACT OF THE DISCLOSURE An extensible,reinforced laminated paper sheet having the characteristic ofwithstanding substantial impacts, formed by two superimposed sheets ofextensible paper bonded together by a layer of hot-melt laminant havinga scrim of polyester iibers embedded therein which transmits stretchingforces through the sheets of paper to points remote from the zone ofimpact to substantially reduce the deformation of the extensible papersheets in the area of impact.

This invention relates generally to reinforced laminated papers, andmore particularly to laminated extensible paper webs which are adaptedto stretch and absorb impacts. Various types of paper webs have beenproposed to lncrease the strength and durability of paper packages orgummed tapes. One such proposal has been the uncreped paper disclosed inCluett Pat. No. 2,624,245, commonly referred to as extensible paper andmanufactured by compressibly shrinking the paper web in the machinedirection, that is, in the direction of web length as the web travelsthrough a web shrinking unit, to produce a built-in stretch in themachine direction (MD), which is adapted to absorb impacts and otherstresses when the paper is used to form packages, containers, tapes andthe like. This paper is adapted to stretch when subjected to impacts orother similar stresses in at least the machine direction, in amountssubstantially in excess of its natural machine direction stretchability,and is also adapted to return to its initial shape after the stretchingforce is removed, providing that the elastic limit of the material hasnot been exceeded. When this limit is exceeded the paper will bepermanently deformed and/or torn.

Extensible paper webs of this type have proved satisfactory for certainapplications, however, it is often desirable to provide paper packagesand the like which are of substantially increased strength and which areadapted to stretch substantially greater amounts than conventionalextensible paper in order to absorb relatively high impacts andstresses.

Accordingly, it is an object of this invention to provide improved paperwebs. A further object of the invention is to provide packagingmaterials for containers and the like which are adapted to withstandabuse in the form of impacting and other stress applications. A stillfurther object of the invention is to provide an impact-resistant webmaterial which is inexpensive in construction, light in weight andmoisture and vapor resistant. Yet another object of the invention is toabsorb impact stresses in packaging material and return the material toits initial configuration after impact.

In accordance with an aspect of this invention a pair of extensiblepaper sheets having machine direction stretchability in excess of theirnatural machine direction stretchability are bonded together insuperimposed relation by a layer of stretchable hot-melt laminantadhesive. A scrim of stretchable polyester iibers is embedded in theadhesive layer between the extensible paper sheets and cooperates withthe sheets or plies of paper to resist deformation under impact orsimilar stresses. The polyester scrim stretches and absorbs the work ofthe impact force and transmits this force through the paper plies awayfrom the point of impact, and, subsequent to the impact, the fibers tendto recover from their stretched condition to draw the paper plies towardtheir original configuration even when the impact stresses aresuiiiciently great to stretch the extensible paper beyond its elasticlimit and normally cause permanent deformation of the paper.

The above, and other objects, features and advantages of this inventionwill be apparent in the following detailed description of illustrativeembodiments of this invention which are to be read in connection withthe accompanying drawings, wherein:

FIG. 1 is a perspective view, with parts broken away, of one embodimentof the invention;

FIG. 2 is a sectional view taken on line 2-2 of FIG. 1, but showinganother embodiment of the invention having a coating of polyethylenematerial; and

FIG. 3 is a sectional view similar to FI'G. 2 of another embodiment ofthe invention.

Referring now to the drawings in detail, and initially to FIG. 1thereof, it will be seen that a reinforced laminated web 10 of the typein which the present invention may be employed generally comprises apair of superimposed sheets or plies of extensible paper 12 and 14 whichare bonded together by an intermediate layer of adhesive 16. Adhesive-16 is, preferably, a hot-melt laminant having the characteristics ofhigh cohesive strength and stretchability. An adhesive of this type,which has been found satisfactory for use in conjunction with thepresent invention, is manufactured and sold by the Paisley Company underthe trade name Paisley T502.

As seen in FIG. 1, a scrim 20 formed by a plurality of fibers isembedded within adhesive layer 16. These fibers are formed of apolyester material which is adapted to stretch when subjected to tensionand has a high elastic limit so that the iibers will recover to .theiroriginal configuration when the tension is released. One group of iibers22 are arranged to extend longitudinally in the machine direction of thepaper, that is, in the direction of web length as the web travelslengthwise through the web shrinking unit and in which thestretchability of the extensible paper is produced. A second group offibers 24 are also embedded in the inner adhesive layer 16 and arearranged in a zig-zag pattern in spaced parallel relation. Each of thefibers 24 is arranged to extend from one edge of sheets 12 and 14 to theopposed edge thereof at an angle of substantially 30 with respect to themachine direction of the web and thereby forms a generallydiamond-shaped pattern within layer 16. The scrim fibers in each of thegroups 22 and 24 of this embodiment may be formed of a polyestermaterial manufactured by the .Fiber Industries Division of the CelaneseCorporation under the designation l000-l92-C-34.

During the manufacturing process of web y10, adhesive layer 16 isapplied to lower sheet 14 at a temperature range of 350 to 370 F. andthe adhesive adheres to both the polyester fibers and sheets 12 and 14to form an integral bond between the various elements of the web. Thelibers 22 and 24 may be embedded in layer 16 during its application tosheet 14 and it is foreseen that the particular pattern of the scrim maybe varied in accordance with the reinforcing desired, as by varying thespacing between iibers or by eliminating either the logitudinallyextending libers 22 or the zig-zag fibers 24.

Web 10, formed by the extensible paper plies or sheets 12 and 14 and thestretchable adhesive layer 16 and fibers 22, 24, comprises an extensiblelaminated structure which is adapted to withstand substantial impact orsimilar stresses and stretch without permanent deformation or rupturingof the material. Webs formed in accordance with the present inventionare particularly adapted for use in constructing paper lbags orcontainers and the like and when these srtuctures are subjected to animpact stress, the polyester fibers 22 and 24 cooperate with the sheetsof extensible paper to stretch and absorb the work of the impact forceand yet return the web to its original configuration and resistpermanent deformation of the package. As web is stretched, polyesterfibers 22 and 24 and extensible paper layers 12 and 14 arecorrespondingly stretched at the point of impact and the fibersdistribute the force of the impact longitudinally along themselves, awayfrom this point, while adhesive layer 16 transmits the distributedimpact force from the fibers to the sheets 12 and 14 at points remotefrom the point of impact. .As a result of this force transfer anddistribution, the stress on plies 12 and 14 at the area of impact ismaterially reduced and therefore there is a substantial reduction in thedeformation of the web. Subsequent to the impact fibers 22 and 24recover from their stretched condition and return to their originalconfiguration. These fibers, being bonded to plies 12 and 14 by adhesivelayer 16, serve to draw the adhesive and the plies back to theiroriginal configuration and thus, even when the impact force issufficient to create permanent damage or deformation in the extensiblepaper, Ias for example, when the paper is stretched beyond its elasticlimit, deformation is held to a minimum since fibers 22 and 24 willreturn the entire structure to its original condition due to itssubstantially higher elastic limit.

IPolyester reinforcing scrims of the character described may be usedwith regular kraft paper to form a reinforced web, or preferably, thesescrims may be used in conjunction with extensible paper of the characterdescribed in the above-mentioned Cluett patent. However, far superiorresults are obtained by the combination of extensible paper with thepolyester reinforced scrim since extensible paper can cooperate with thepolyester due to its stretchability characteristics. Moreover, thecombination of polyester fibers and extensible paper substantiallyincreases the stretchability of the web and increases the toughness ortensile strength of the composite web in the machine direction of thepaper sheets. Table I shows a comparison between the use of polyesterreinforcing scrim in conjunction with both regular lkraft paper andextensible paper, wherein 4both a one-way pattern and diamond-shapedpattern of the scrim were utilized.

TABLE I ONE-WAY PATTERN MD toughness, MD ft. percent DesignationConstruction lbs./ft.2 stretch Polyester 2 plies 0f 40 lb. regularkraft, 30 lb. of 10 reinforced hot-melt laminant, Paisley 7502, paper.applied at 350-370 F. Reinforcing: Polyester ber, Fiber Industries,1000-192-0-34 2 fibers/in. machine direction only. Polyester 2 plies of40 lb. Extensible kraft, 30 44 11 reinforced lb. of hot-melt laminant,Paisley extensible 7502, applied at 350-370 F, Reinpaper. forcing: FiberIndustries, 1000- 192-0-34 2 fibers/in. machine direction only.

DIAMOND PATTERN Polyester 2 plies of 40 lb. Regular kraft, 30 lb. 13 2reinforced of hot-melt Paisley 7502, applied paper. at 350-370 F.Reinforcing: Polyester ber, Fiber Industries, 1000- 192-0-34 1 ber/in.zig-zag, 2 bers/in. MD Polyester 2 plies of 40 lb. Extensible kraft, 3045 11 reinforced 1b. of hot-melt Paisley 7502 applied extensible at350370 F. Reinforcing: Polypaper. ester ber, Fiber Industries, 1000-192-0-34 1 ber/in. zig-zag. 2 fibers] in. MD.

As is evident from the above table the machine direction toughness ortensile strength of the reinforced laminated web produced in accordancewith the present invention is substantially increased when a combinationof extensible kraft paper and polyester scrim are utilized.

This increase in toughness gives far superior strength to packages orthe like produced by this material. In addition, the percent of stretchor elongation of the weby is also increased, and this characteristicpermits the package to absorb greater impact forces and yet resistdeformation, that is, to absorb the impact force and yet return to itsoriginal configuration without a permanent deformation or bulge in thepackage.

FIG. 2 illustrates another embodiment 30 of a reinforced laminated webaccording to the present invention wherein a pair of extensible papersheets 12 and 14 are bonded together by a layer of adhesive 16 havingembedded therein a scrim 20 formed by polyester fibers 22 and 24 insubstantially the same manner as illustrated in the embodiment found inFIG. l. Web 30 in this embodiment however, is provided with a protectivecoating o r sheet of polyethylene 32 which protects the web from wateror other moisture. Sheet 32 is stretchable so that it acts as an activecomponent of laminated sheet 30 and stretches with the web when it issubjected to impacts or similar stresses. This embodiment is adapted tobe used in the manufacture of waterproof multi-wall bags; the basicWeight of top and bottom extensible kraft plies 12 and 14 in thisembodiment may be 40 lbs. and 50 lbs. respectively, whereas thepolyethylene sheet is between one-half to two mils thick. As with theprior embodiment, the longitudinally extending reinforcing fibers 22 maybe omitted when the additional strength that they supply is notrequired.

Reinforced laminated webs formed in accordance with the presentinvention are also admirably fitted for use as high strength gummedtape, and such a tape is illustrated in FIG. 3. As seen therein, tape 40has upon one surface, for example, the lower surface of sheet 14, alayer 42 of adhesive material which is adapted to be activated by waterin the conventional manner. The basic weights of the two sheets 12 and14 in this embodiment may typically be 30 and 40 lbs. respectively,although it is contemplated that other combinations of weights for thesesheets may advantageously be utilized.

Although illustrative embodiments of the invention have been describedherein with reference to the accompanying drawings, it is to beunderstood that the invention is not limited to those preciseembodiments, and'that various changes and modifications may be effectedtherein by one skilled in the art without departing from the scope orspirit of this invention.

What is claimed is:

1. A laminated reinforced web comprising two sheets of kraft paperbonded together in superimposed relation by a layer of stretchableadhesive material and a plurality inf stretchable polyester fibersembedded in said adhesive ayer.

2. A laminated reinforced web as defined in claim 1 wherein each of saidsheets of kraft paper consists of extensible uncreped kraft paper havingmachine direction stretchability in excess of its natural machinedirection stretchability.

3. A laminated reinforced web as defined in claim 2 wherein saidstretchable polyester fibers define a scrim between said sheets ofpaper.

4. A laminated reinforced web as defined in claim 3 wherein said fibersextend longitudinally in the machine direction of said sheets of paper.

5. A laminated reinforced web as defined in claim 3 wherein said fibersare arrayed in a zig-zag pattern with respect to the machine directionof said sheets of paper.

6. A laminated reinforced web as defined in claim 5 wherein each of saidzig-zag bers forms an angle of substantially 30 to the machine directionof said sheets of paper.

7. A laminated reinforced web as defined in claim 3 wherein said fibersconsist of two groups of fibers, the fibers in said first groupextending generally longitudinally with respect to the machine directionof said sheets and the fibers in said second group being arrayed in azig-zag pattern with respect to said machine direction.

8. A laminated reinforced web as defined in claim 3 wherein one of saidsheets of paper is coated with a water impermeable layer of plasticmaterial to waterproof said web.

9. A laminated reinforced web as defined in claim 3 wherein one of saidsheets of paper is coated with an adhesive material.

10. A laminated reinforced web comprising two sheets of extensible kraftpaper having a machine direction stretchability in excess of its naturalmachine direction stretchability and bonded together in superimposedrelation by a layer of stretchable hot-melt laminant adhesive, saidlayer including a plurality of stretchable polyester fibers embeddedtherein forming a scrim between said sheets of paper whereby said web isadapted to stretch and absorb impacts and similar stresses.

11. A method of producing a stretchable reinforced web comprising thesteps of, applying a layer of adhesive material having a plurality ofstretchable polyester fibers therein to a first sheet of extensiblekraft paper and supereY imposing a second sheet of said extensible kraftpaper on said layer.

12. A method as defined in claim 11 including, the step of, arrangingsaid fibers to extend longitudinally in the machine direction of saidsheets of paper.

13. A method as defined in claim 11 including, the step of, arrangingsaid fibers in a generally zig-zag pattern with respect to the machinedirection of said sheets of paper.

14. A method as defined in claim 11 including, the steps of, arrangingcertain of said fibers to extend longitudinally in the machine directionof said sheets of paper and arranging the remainder of said fibers in agenerally zig-zag pattern with respect to said machine direction.

1S. A method as defined in claim 11 including the step of, coating oneof said sheets of paper with a water impermeable layer of plasticmaterial.

16. A method as defined in claim 11 including the step of, coating oneof said sheets of paper with an adhesive material.

References Cited UNITED STATES PATENTS 2,902,395 9/1959 Hirschy et al161-143 3,444,024 5/ 1969 Hillas 161-89 X 3,519,509 7/1970 Gidge et al.161-156 X 3,161,560 12/1964 Paquin et al 161-270 X ROBERT F. BURNETT,Primary Examiner M. A. LITMAN, Assistant Examiner U.S. C1. X.R.

Disclaimer 3,671,372.Paul Hojman, Gainesville, F1a. LAMINATED PAPER WITHRE- INFORCING SCRIM. Patent dated June 20, 1972. Disclaimer filed Sept.13, 1982, by the assignee, Georgia-Pacific Corp. Hereby enters thisdisclaimer to claims 1, 10, 11, 12, 13, 14, l5 and 16 of said patent.[Official Gazette November I6, 1982.]

